What is not an advantage of using a light-duty, low-voltage circuit to control relays?

The statement that the lights will not be as bright with lower voltage is indeed not an advantage of using a light-duty, low-voltage circuit to control relays. In this context, light-duty low-voltage circuits are often used for control purposes, where the primary focus is on safety, cost reduction, and ease of modification rather than on the brightness of lights.

When a circuit operates at a lower voltage, it typically means that the power delivered to the load (like lights or motors) will be less than if it were operating at a higher voltage. Therefore, while the circuit may be safer and more cost-effective to install and modify, it may also result in decreased performance, such as dimmer lights. This aspect of lower voltage circuitry—where the output power and thus the brightness can be lower—makes it clear that this is not an advantage.

In contrast, the benefits of using low-voltage control systems include reduced installation costs due to the possibility of using less robust wiring (which can be run without conduit), simpler and more economical alteration work, and the ability to control more complex systems without the risk of high voltage safety issues. The full voltage circuitry being shortened can also enhance safety and reliability. Thus, while the other aspects highlight clear advantages